Evaluation of Epigallocatechin-3-gallate (EGCG) Modified Collagen in Guided Bone Regeneration (GBR) Surgery and Modulation of Macrophage Phenotype

Collagen membranes have been widely applied for guided bone regeneration (GBR), a technique often utilized in dental implant surgery for bone argumentation. However, the implantation of collagen membranes also elicits foreign body reaction (FBR), the imbalance of which may lead to failures of dental implants. Macrophages play a pivotal role in FBR as macrophages can polarize into pro-inflammatory (M1) and pro-regenerative (M2) phenotypes. Therefore, collagen membranes based on modulation of macrophage polarization have gained increased attention. Epigallocatechin-3-gallate (EGCG)-modified collagen membranes have been previously shown to downregulate the expression of inflammatory factors. In the present study, scanning electron microscopy images showed that EGCG-modified collagen membranes prevented the migration of keratinocytes and maintained space for osteoblasts. CCK-8 and live/dead cell assays showed that EGCG-modified collagen membranes unaffected the cell viability of osteoblasts. In addition, immunofluorescent staining and quantitative real-time polymerase chain reaction showed an increased number of M2 macrophages, an upregulated expression of growth factors including vascular endothelial growth factor, bone morphogenetic protein 2, and an upregulation of osteogenic differentiation-related factors including Runt-related transcription factor 2 and osteopontin after implantation of EGCG-modified collagen membranes. Hematoxylin-eosin staining and Micro-CT further demonstrated that the application of EGCG-modified collagen membranes promoted new bone formation in vivo. From these findings it is concluded that EGCG-modified collagen membranes have promising potentials in GBR surgery which served as suitable barrier membranes and promoted bone regeneration in vivo by recruiting M2 macrophages, promoting secretion of growth factors and osteogenic differentiation.